In prior art systems, a central management function is implemented in either the first or second communication system. If implemented in the first communication system the first terminal may be granted the PTT session (if resources are available) almost directly. However, when the central management function is implemented in the second communication system, the first terminal will have to wait a long period before receiving a grant of a PTT session, due to the required double traverse of the transmission link. If the delay of the transmission link is long (e.g. when using satellite communications), this long period may be longer than acceptable.